Ceramics-Silikáty 65, (4) 344 - 353 (2021)

In this study, red mud was used to synthesis of calcium sulphate anhydrite (CSA) self-doped with SiO₂ for production bioceramic. The agitation sulphuric acid leaching method was used at atmospheric conditions to synthesis of CSA powder that was pressed as green body pellets for sintering procedure at a temperature varying from 800 °C to 1200 °C. After sintering, mechanical, chemical and in vitro tests were performed to determine the optimum parameters for bioceramic production. The in vitro tests were conducted to determine the biodegradability and bioactivity characteristics of sintered-CSA (S-CSA). CSA powder was synthesized at optimum leaching parameters (95°C, 14M H₂SO₄, 0.10 (w/v), 180 min.), its mineralogical composition was CSA (97.9%) and SiO₂ (2.1%). Density, compressive strength and hardness were reached 2.65 g/cm³, 114.67 MPa and 149.20 HV, respectively at 1100 °C of S-CSA pellets. As the temperature increased wollastonite/larnite phases formed. The homogenous bone-like structure hydroxyapatite phase was detected at 28th day of the in vitro test. As a conclusion, bioactive CSA self-doped with SiO₂ could be produced directly from red mud in a single step, without using additional substances and that was obtained to ensure the use as a bioceramic.